Japanese Patent Application Publication No. 2000-153958 discloses a sheet post-processing apparatus for performing stitching and folding processes.
In the sheet post-processing apparatus, a sheet positioning member movable up and down for receiving the leading edge of each sheet in the conveying direction, a stapler unit for stitching a sheet bundle stored in the sheet positioning member, a folding roller pair for folding the stitched sheet bundle, and a folding drive mechanism having a projection unit are arranged sequentially downward from above. When sheet bundles for each document are all loaded by the sheet positioning member, they are stitched by the stapler unit. Thereafter, the sheet positioning member is moved, thus the sheet bundles are moved to the position of the folding drive mechanism, and the folding roller pair and projection unit perform the folding process. The folding drive mechanism pushes the sheet bundle pushed by the projection unit into the nip portion of the folding roller pair from one side, holds under pressure and discharges it from the opposite side, and then book-binds and loads it on the receiving tray.
However, the apparatus aforementioned performs the stitching process for the sheet bundle and then performs the folding process, so that the sheet positioning member must move from the position where the sheet bundle is subjected to the stitching process to the position where the folding process is performed. Further, when processing a plurality of sheet bundles, the sheet positioning member must return from the position where the folding process for the sheet bundle performs to the position where the stitching process performs again. Therefore, the processing of the sheet bundles takes a lot of time.
Further, in the apparatus aforementioned, the sheet positioning member supports the sheet bundle while processing one sheet bundle. Therefore, until the bookbinding process of the sheet bundle is completed, the succeeding sheets cannot be conveyed, thus when processing a plurality of sheet bundles, a problem arises that the throughput until completion of all the jobs is not good.
Further, in the apparatus aforementioned, the stitching process is performed for sheets in correspondence to the number of job copies and then the folding-in-two process is performed, so that when heavy paper is used, the number of sheets cannot be increased. Further, if glossy paper is used, when holding under pressure and conveying them by the folding roller pair, between the overlaid sheets, slipping occurs and a problem arises that the outside sheet in contact with the rollers slips and is conveyed prior.
Further, in the apparatus aforementioned, the sheet conveying path during loading, stitching, and folding the sheets is arranged almost perpendicularly, so that a problem arises that the apparatus is enlarged in the longitudinal direction. Furthermore, to perform the folding process for a heavy paper bundle, a strong structure is necessary and a problem arises that the apparatus is enlarged.